In a message dated 7/20/01 8:27:01 AM Pacific Daylight Time, kq2m@mags.net
writes:
> My thought is to have all the cables come out of the tower under the bottom
> rung, go to a metal box next to the tower, be grounded there,
What's the purpose of the metal box?
Commercial specs call for grounding cables that come down the tower
*before* they turn towards the building. The cables should be grounded
directly to the tower at that point to offer the lowest resistance path to
ground. The bend in the cables introduces inductance at that point so you
want to be grounded before that so the lightning energy will go there to
ground.
> and then
> proceed at about the 4' level (near the tower) taped around a steel guy
wire
> (as a messenger cable for support) and anchored at the house at about 12'
> above ground (slight downward slope from tower) where the cables will then
> be routed to another metal box (and grounded again) and then proceed inside
> to the shack to an aluminum panel with disconnects.
The idea is to keep the lightning energy OUT of the house so either your
aluminum panel needs to be outside the house or you need a bus bar at the
building entry where the cables are grounded before they go inside. (I hope
it's obvious that the bus bar is grounded.) The outside entry bus bar is the
focal point of your Single Point Ground System. It's where all the ground
wires meet.
>
> The aluminum panel will be grounded to the outside metal box with thick
> solid copper wire through a hole in the side of the house which the cables
> will also pass through.
The aluminum panel only needs to be connected to the outside bus bar to
be part of the ground system.
I don't know what the purpose of the outside metal box is. If it's for
some sort of grounding function, it will put more resistance in the system
and the charge will find an another path to ground - most likely one you
hadn't planned on. That's why you need the cables grounded at the bottom of
the tower before they turn towards the building.
Cheers, Steve K7LXC
Tower Tech
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